why can't you convert a fly reel to centerpin?

Centerpin Float Reel & Fly Reel Bearing Replacement

Center Pin Question? Washington Fly Fishing Forum

Float Reel Centre PIN Reel Steelhead Fishing COARSE

Are expensive Fly Reels over rated?

Ideal Nymph Reel

talk to me about center-pinning

Types of Fishing Reels: The Angler's Handbook

Fly Reel Blues, Global FlyFisher

Float Reel Centre PIN Reel Steelhead Fishing COARSE

Centerpin Reels

Shakespeare SPEEDEX Center Pin Fly Fishing Reel. Diameter 3 1/2 inch

NGT Dynamic Centrepin Reel, Fishing Reel : : Sports & Outdoors

Okuma Sheffield Centre Pin Reel

3½ Amirantes Reel, by Richard Carter (Pre-owned) – Ireland's Antique Fishing Tackle